This invention relates generally to a device for use in ophthalmic surgery with a specific application to intraocular surgery. This invention consists of novel features which will help a surgeon in performing surgeries on lens disorders such as cataracts. Specifically, the present invention relates to a surgical knife for making a continuous, smooth, curvilinear, stress-free, tag-free cut of the anterior lens capsule required in extracapsular cataract surgery. This invention is unique and novel in that it permits the surgeon to manually and positively position the blade at a desired angular position during movement of the surgical instrument's handle.
An individual's vision depends upon the eye forming an image of an object and sending that image to the sensory centers of the brain. Image formation involves the following process: an object will reflect light through the cornea, the aqueous humor, the pupil, the lens, and the vitreous humor of the eye; the reflective light is then focused by the lens onto the retina. The nerve fibers within the retina collectively leave the eye in the optic nerve and enter the brain where the visual signals are processed.
However, the lens and its ability to form an image is subject to physical damage due to lens disorders such as the formation of cataracts. Lens deficiencies, such as cataracts, are generally treated by performing cataract extraction wherein an opening is provided in the anterior lens capsule through which the lens opacity is removed. This procedure involves removal of the opaque crystalline lens substance after opening the anterior lens capsule by an anterior capsulectomy. The anterior capsule is a cellophane-like membrane covering the anterior surface of the lens.
A variety of devices have been created to cut or tear the anterior capsule. The most common device used today for an anterior capsulotomy is a cystotome. When cataracts are removed by an extracapsular extraction method, a cystotome is inserted through a small incision in the sclera or peripheral cornea and small connecting tears are made in the anterior lens capsule in a circular pattern around the periphery of the lens capsule. When a complete circle has been made by connecting the tears, a circular piece of the anterior capsule is free to be removed. For extracapsular cataract extractions, this method is sufficient and desirable.
The phacoemulsification method of cataract removal requires a different type of anterior capsular opening. During phacoemulsification, there is a great deal of tension on the cut edges of the anterior capsule while the lens nucleus is emulsified with ultrasound energy. For this method, a tagless, continuous cut or tear is a critical step for safe and effective phacoemulsification. If the capsule is opened with numerous small capsular tears, as in the extracapsular technique, the small tags which remain can lead to capsular tears which can extend posteriorly to the posterior capsule. Such a radial tear is a complication because it destabilizes the lens for further cataract removal and safe intraocular lens placement within the lens capsule later in the operation. More importantly, once the posterior capsule is punctured, the vitreous humor behind it gains access to the front of the eye. If the vitreous enters the front of the eye through a hole in the posterior capsule, the vitreous must be removed by an additional procedure with special instruments. This vitreous loss is associated with an approximate increase two times in the rate of subsequent retinal detachment and in increased risk of endophthalmitis or infection within the eyeball; both complications are potentially blinding.
The methods which are currently employed for producing a continuous curvilinear capsular opening are quite difficult to control by the surgeon. The standard method begins with a capsular incision which is made with a cystotome. This incision is then coaxed to form a circular or oval shape by pushing the leading edge of the freshly tearing capsule with the cystotome in a non-cutting fashion, or the initial capsular incision is torn into a circular shape by grasping the leading edge with fine caliber forceps. This is a very challenging maneuver and even in the most experienced hands, the tearing motion can lead to an undesirable tear of the capsule toward the back of the lens.
Even if a proper tagless edge is produced, the capsular opening's size or position is often not ideal. A small capsular opening can impair the safe removal of the lens nucleus and cortex and prevent proper intraocular lens insertion into the lens capsule. The additional stresses placed on the lens capsule, which results from having to work with a small or eccentric capsular opening, puts the eye at risk for zonular and capsular breakage. Both of these breakages will prolong the operative time and can lead to vitreous loss.
Some of the prior devices used in performing an anterior capsulectomy include manual and mechanical techniques for severing the anterior lens capsule of the eye. For example, U.S. Pat. No. 4,570,632 to Woods describes a cystotome which produces a continuous series of perforations; U.S. Pat. No. 4,706,669 to Schlegel describes a device for perforating the lens capsule by use of a wire which is connected to a drive motor which causes the wire to engage in an auxiliary reciprocating motion; U.S. Pat. No. 4,708,138 to Pazandak describes a manually rotating surgical cutting knife; and U.S. Pat. No. 4,885,004 to Pao describes a rotating cystotome.
In most prior known devices, it is difficult to cleanly cut the capsule without leaving residual "tags" or tears in the capsule. Moreover, these devices either cause sufficient drag on the capsule and rock the nucleus of the lens, or place stress on the zonular structure. More importantly, none of the prior devices allows the surgeon to positively position and control the blade at a desired angular position during the movement of the blade's handle. Rather, the configuration of the lens directs the path and angle of the blade disclosed in the prior devices. In other words, these prior devices are directed passively by frictional contact with the lens substance. In addition, these prior devices require a high level of skill, have a protracted learning time, and a significant amount of experience with these devices is necessary to consistently obtain successful results.
The problem which forms the basis of this invention consists in developing a device that permits the surgeon to make a continuous, smooth, curvilinear cut by manually and positively changing the blade's angle of attack through a controller on the handle. The need to enhance the methods and procedures for performing the anterior capsulectomy during phacoemulsification surgery has become critical to the success of the surgery. As a result of the difficulties and complications discussed above, a definite need exists for a device that allows the surgeon to adjust and control the blade's angle of attack in an efficient, effective and complication-free manner. It is, therefore, a feature of the present invention to provide a capsulectomy apparatus which manually facilitates a continuous, smooth, curvilinear cut.
Another feature of the present invention is to provide a capsulectomy apparatus which does not rock the nucleus of the lens.
An additional feature of the present invention is to provide a capsulectomy apparatus that eliminates residual tags of the anterior capsule.
A further feature of the present invention is to provide a capsulectomy apparatus which easily cuts any desired capsule pattern, at any location, and of any size.
To achieve the above objects, features, advantages, an ophthalmic surgical device is provided which comprises a handle, a blade rotatably mounted to the handle's distal end and a controller on the handle for manually and positively positioning the blade at a desired angular position during movement of the handle. The controller can consist of a variety of different mechanisms such as two opposed jaws that move relative to each other; or a plurality of spools which are connected by a bell: and the rotation of one spool permits the surgeon to control the blade's angle of attack; or an operator and gear train which transmits the operator's motion to the blade. The surgical instrument also includes an orientation mark on the blade which indicates the plane of the cutting blade.
Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.